Location: Crop Production Systems Research2021 Annual Report
1. Determine differences in seed biology and fitness characteristics, such as competitiveness, photosynthetic capacity, responses to stress, and other growth- related factors of herbicide-susceptible versus herbicide-resistant weed biotypes. 1A. Determine differences in fitness characteristics, such as competitiveness, photosynthetic capacity, and responses to stress factors in herbicide-susceptible versus herbicide-resistant weed biotypes. 1B. Determine differences in fitness characteristics, such as competitiveness and responses to stress factors in herbicide-susceptible versus herbicide-resistant weed biotypes. 1C. Determine differences in fitness characteristics, photosynthetic capacity, and responses to stress factors in herbicide-susceptible versus herbicide-resistant weed biotypes. 1D. Comparison of whole-plant physiological processes of herbicide resistant weed populations with corresponding susceptible populations. 1E. Comparison and characterization of pigment contents and antioxidant capacities of red and green biotypes of glyphosate-resistant Palmer amaranth plants and their responses to selected herbicides and a bioherbicide. 2. Discover and characterize patterns of herbicide resistance in weed populations, elucidate underlying physiological, biochemical, and molecular mechanisms for use in identifying unique biological features that define their “weediness”, and explore their utility for developing control strategies. 2A. Discover and characterize patterns of herbicide resistance in weed populations. 2B. Elucidate underlying physiological, biochemical, molecular mechanisms of resistance to herbicides in weed populations where the level and nature of resistance is known. 2C. Discover and develop new approaches to weed control based on development of molecular herbicides specifically targeting our most troublesome weeds. 3. Identify key additive and/or synergistic interactions of combinations of chemicals, natural products and/or plant pathogens with herbicides to manage or control herbicide resistant weeds. 4. Evaluate for efficacy novel herbicide drift management and application techniques, emerging commercial herbicide or herbicide resistant crop technologies, and weed control methods such as microwave and steam. 4A. Evaluation of a novel fluorescent compound for measuring herbicide drift. 4B. Evaluation of unmanned aerial vehicle (UAV) technology for detection and management of herbicide-resistant weed populations and herbicide drift issues. 4C. Evaluation of emerging commercial herbicide and or herbicide resistant crop technologies. 4D. Evaluate the efficacy of microwave weed control methods.
The overall project goal is to discover basic and practical knowledge of the occurrence, distribution, mechanism of resistance and management of weeds that are difficult to control or that have evolved resistance to one or to multiple herbicides. This broad-scope approach will lead to more effective weed control methods and novel weed control management practices. The development of new weed management tools, aided by knowledge of resistance mechanisms and weed biology will advance the development of sustainable practices for early detection and management of weeds and facilitate the development of strategies to provide more efficacious weed control via integrated use of chemical, mechanical, biological and cultural methods. Through basic analyses, assays and bioassays of whole plants and plant tissues from laboratory, greenhouse and field experiments will determine major differences in resistant versus susceptible weed biotypes. Subsequent biochemical, genetic, proteomic, immunochemical and radiological studies will identify and characterize specific site differences in herbicide resistant and sensitive weed biotypes within species. Experiments on the development of novel mechanical weed control methods and weed control using bioherbicides will provide important results that could substantially lower the amount of herbicide usage. The knowledge generated from these experiments will provide a greater understanding of the biochemistry, physiology and genetics of resistance mechanisms and provide insight for recommendations that will promote efficacious and sustainable weed control coupled with more efficient and economic crop production with reduced herbicide usage and impact on the environment.
Interactions and effects of aminooxyacetate and boc-aminooxyacetate on cysteine synthase activity and on two bioherbicides (Colletotrichum truncatum and Alternaria cassia) and their weed hosts (hemp sesbania and sicklepod, respectively) were evaluated and the results published. The effects of two formulations of glyphosate (WeatherMax® and Engame™) were compared on cotyledon surface structure, chlorophyll A fluorescence and shikimate levels in isogenic cotton cultivars differing in roundup (glyphosate) resistance. Results were summarized and published. The host range and virulence of a fungal pathogen for biocontrol of giant salvinia (Salvinia molesta) was defined and results published. Autonomous replication sequences (ARS) from the Amaranthus palmeri eccDNA replicon enable replication in ARS-deficient yeast. This established the presence and capacity of autonomous replication sequences in the replicon to support independent replication. A plant pathogen and candidate bioherbicide CABI-IMI 368023 (previously identified as Myrothecium verrucaria), has been extensively studied in our laboratory and was recently analyzed morphologically and genetically and found to be most consistently aligned with representatives of Albifimbria verrucaria. The results are important since the classification of this weed biocontrol agent is more accurately defined in relation to other microorganisms. Resistance to acetolactate synthase inhibitors was found to be caused by a W 574 to L amino acid substitution in the ALS gene of redroot pigweed and tall waterhemp from Mississippi. A study of the homogeneity among replicons in glyphosate-resistant Amaranthus palmeri in geographically distant locations was completed and published demonstrating the extreme conservation of sequence across the nation.
1. Characterization of a replicon that causes resistance to glyphosate. ARS researchers in Stoneville, Mississippi, and Clemson University, continued research on the replicon in Palmer amaranth, the entity conferring resistance to glyphosate in Palmer amaranth. They discovered the presence of miniature, circular, genetic elements of sufficient quantity to encode the entire replicon in resistant plants. Glyphosate-sensitive plants also contain miniature circular elements but are insufficient in number and quality to synthesize a complete replicon. Characterization of this replicon is important in detailing the molecular mechanism involved in resistance.
Molin, W.T., Bowling, A.J., Vaughn, K.C. 2020. Comparison of WeatherMax® and Engame™ formulations of glyphosate on cotyledon surface structure, chlorophyll A fluorescence and shikimate levels in isogenic cotton cultivars differing in Roundup resistance. American Journal of Plant Sciences. 11:1193-1205. https://doi.org/10.4236/ajps.2020.118084.
Molin, W.T., Yaguchi, A., Blenner, M., Saski, C.A. 2020. Autonomous replication sequences from the Amaranthus palmeri eccDNA replicon enable replication in yeast. BMC Research Notes. 13:330. https://doi.org/10.1186/s13104-020-05169-0.
Molin, W.T., Saski, C.A., Patterson, E.L. 2020. Homogeneity among glyphosate-resistant Amaranthus palmeri in geographically distant locations. PLoS ONE. 15(9):e0233813. https://doi.org/10.1371/journal.pone.0233813.
Nandula, V.K., Giacomini, D.A., Molin, W.T. 2020. Target site-based resistance to ALS inhibitors, glyphosate, and PPO inhibitors in an Amaranthus palmeri accession from Mississippi. American Journal of Plant Sciences. 11:1206-1216. https://doi.org/10.4236/ajps.2020.118085.
Boyette, C.D., Hoagland, R.E., Higgenbotham, L.R., Walker, H.L., Young, J.A., Stetina, K.C. 2021. Host range and virulence of a fungal pathogen for control of giant salvinia (Salvinia molesta). American Journal of Plant Sciences. 12:444-454. https://doi.org/10.4236/ajps.2021.123029.
Nandula, V.K., Giacomini, D.A., Ray, J.D. 2020. Resistance to acetolactate synthase inhibitors is due to a TRP 574 to LEU amino acid substitution in the ALS gene of redroot pigweed and tall waterhemp from Mississippi. PLoS ONE. 15:6. https://doi.org/10.1371/journal.pone.0235394.
Hoagland, R.E., Hirase, K., Boyette, C.D. 2021. Interactions and effects on cysteine synthase activity of aminooxyacetate and boc-aminooxyacetate on the bioherbicides collectrotrichum truncatum and alternaria cassia and their weed hosts. American Journal of Plant Sciences. https://doi.org/10.4236/ajps.2021.125052.